Jason Bay is still undergoing tests, but there are early indications the concussion he sustained last week is not as severe as the one that cost him the final two months of the 2010 season, a team source said Friday. The Mets left fielder visited with teammates before Friday night's 6-4 win over the Yankees at Citi Field — his first trip back since hitting his head on the left-field fence eight days ago and staggering from the field with a concussion. The source said many of Bay's symptoms have subsided, and there is a sense of optimism he won't need to miss the remainder of the season — as some within the organization had originally feared. But Bay is under continued evaluation by doctors. Bay's previous concussion came in July 2010, when he smashed into the left-field fence at Dodger Stadium.